APPARATUS FOR STIMULTANEOUS INOCULATION OF A SET OF CULTURE TUBES.

Abstract

T h e work of inoculating large numbers of culture tubes when applying diagnostic or tasono~nic tests to bacteria is often tedious and time-consuming. Multipoint devices for the inoculation of plate cultures have been described (e.g. 1 , 8, 9) . This note describes a multipoint i ~ ~ o c u l a t o r and ancillary apparatus designed for use in test procedures which require the transfer of i~loculum fro111 tube to tube. T h e apparatus enables up to 60 inoculations to be performed in a single transfer-operation. I t is not intended for use in the transfer of stoclc cultures. Some examples of test procedures in which this device has been successfully used arc given below, following the description of the apparatus. T h e apparatus comprises a multipoint inoculator (Fig. 3, F j , a t least two guide frames (Fig. 2 , C), and a number of tube racks (Fig. 1, A) together with capholders (Fig. 1 , B). The multipoint inoculator co~lsists of a 1/16-in. brass plate with handles on its upper surface. On its lower surface stainless steel needles (4 in. X 3/16 in. No. 1 , annealed and ground) are set a t right angles and are spaced 1 in. apar t in six rows of 10 needles (Fig. 3, H). At each of the four corners of the brass plate is a 0.24 in. X 5-1/4 in. brass rod (Fig. 3, G ) which engages in corresponding 0.25 in. internal diameter brass tubes (Fig. 3 , I) located one a t each corner of the rectangular (11-3/16 in. X 6-3/16 in.) guide fl-ame. These four tubes position the inoculator accurately over the culture tubes. T h e guide frame consists of a rectangular base, made from 1/16 in. brass plate with the brass guide tubes set a t right angles on it. Two small tapered brass pegs protrude 3/4 in. from the floor of the guide frame, in the center line, and engage in corresponding holes in the base of each tube rack. These pegs position the rack accurately within the guide frame. The respective lengths of the corner rods on the inoculator (Fig. 3, G) and of the matching corner tubes on the guicle frame (Fig. 3, I ) together determine the length of inoculating needle which enters the tubes and , in con j~~nc t ion with the volunle of medium ~ ~ s e d , determine the depth to which the inoculating needles penet ra te the medium. T h e tube raclts, of 24-gauge stainless steel, are 6-1/2 in. X 10-1/2 in. X 3-1/4 in. overall, and contain six rows of ten 31/32 in. diameter holes, whose centers are accurately positioned a t a distance of 1 in. fro111 each other and which correspo~ld to the position of the needles of the multipoint inoculator. Accompanying each rack is a capholder (Fig. 1 , B). This 24-gauge stainless steel t ray (1/4 in. X 6-1/12 in. X 10-1/2 in.) contains six rows of ten 3/4 in. diameter holes, also located on 1 in. centers to correspond with the holes in the tube rack (Fig. 2, D). T h e skirts of Bacti-Capall, 16 mm polypropylene